CN112453413B

CN112453413B - Preparation method of oxide dispersion strengthening steel spherical powder for 3D printing

Info

Publication number: CN112453413B
Application number: CN202011308590.6A
Authority: CN
Inventors: 李少夫; 杨亚锋; 崔景毅; 胡超权; 王宇枭
Original assignee: Zhongke Nanjing Green Manufacturing Industry Innovation Research Institute; Institute of Process Engineering of CAS
Current assignee: Zhongke Nanjing Green Manufacturing Industry Innovation Research Institute; Institute of Process Engineering of CAS
Priority date: 2020-11-20
Filing date: 2020-11-20
Publication date: 2023-05-12
Anticipated expiration: 2040-11-20
Also published as: CN112453413A

Abstract

The invention relates to a preparation method of oxide dispersion strengthening steel spherical powder for 3D printing, which comprises the following steps: (1) Mixing the gas atomization prealloy powder and the rare earth oxide powder, and then performing high-energy ball milling to obtain oxide dispersion strengthening steel powder; (2) And mixing the obtained oxide dispersion strengthening steel powder with an air flow grinding medium, adding the mixture into a fluidized bed, and discharging air in the fluidized bed to obtain a material-carrying fluidized bed. (3) And heating the obtained carrying fluidized bed and introducing mixed gas, controlling the flow of the mixed gas after the fluidization state of the powder in the carrying fluidized bed is stable, and cooling after the preset reaction time is reached, thereby obtaining the steel ball-shaped powder from the carrying fluidized bed. Has the advantages of simple preparation process, low production cost, high efficiency, less impurity introduction amount, easy realization of engineering amplification, and the like, has sphericity of more than 75d1/da, granularity of 10-100 mu m, fluidity value of less than 20s/50g and oxygen content of less than 3500ppm.

Description

Preparation method of oxide dispersion strengthening steel spherical powder for 3D printing

Technical Field

The invention relates to the field of 3D printing, in particular to a preparation method of oxide dispersion strengthening steel spherical powder for 3D printing.

Background

The oxide dispersion strengthening steel has the advantages of good high-temperature creep property, excellent irradiation damage resistance, high tissue stability in extreme environment and the like, and is considered as an ideal candidate material for key parts of a fourth-generation nuclear reactor. The excellent mechanical property and the tissue stability of the nano-oxide mainly originate from nano-oxide particles dispersed in the matrix, the metal matrix is strengthened by pinning dislocation and grain boundary, and the irradiation damage is restrained by high-efficiency capturing of defects such as irradiation cavities, helium bubbles and the like. The traditional preparation route of the oxide dispersion strengthening steel is to mechanically alloy prealloy atomized powder and nanometer yttrium oxide by adopting high-energy mechanical ball milling, then to shape the mechanically alloyed powder by adopting hot isostatic pressing or hot extrusion, and then to obtain the oxide dispersion strengthening steel product by fusion welding and machining. However, nano oxide particles are easy to agglomerate and grow up or burn to slag in the welding process of the oxide dispersion strengthening steel, so that the performance of the welding area of the oxide dispersion strengthening steel product is seriously degraded, and the oxide dispersion strengthening steel product cannot be safely served in a severe nuclear reactor in an operating environment.

The metal 3D printing is a novel near net forming technology for manufacturing parts by accumulating materials layer by layer, has the advantages of cost saving, high-degree-of-freedom design, high-precision forming and the like, has been widely used in scientific research and production of materials such as stainless steel, titanium alloy, aluminum alloy and the like, and the printed parts thereof are gradually applied to verification in the fields of aerospace, biomedical treatment, national defense technology and the like. As CN105364065a discloses a metal powder for 3D printing and a preparation method thereof, and a 3D printing method, the preparation method of the metal powder for 3D printing comprises the following steps: iron-based alloy powder with the particle size of 20-60 microns is taken as a matrix, iron oxide powder with the particle size of 50 nanometers-2 microns and carbon powder are taken as additives, and the metal powder is obtained by uniformly mixing; the ratio of the mass of the iron oxide powder to the mass of the carbon powder is in the range of 4.4:1-8.8:1, and the ratio of the sum of the mass of the iron oxide powder and the mass of the carbon powder to the mass of the iron-based alloy powder is in the range of 1:100-1:400. After the metal powder is prepared, printing the metal powder into a three-dimensional blank by adopting a 3D printing method of micro-jet bonding; and degreasing and sintering the three-dimensional blank at the sintering temperature of not lower than 900 ℃ to obtain the 3D printing product. The metal powder provided by the invention is used for printing products prepared by a 3D printing method, and has higher density.

CN110499463a discloses a method for preparing 316L stainless steel 3D printing metal powder by reducing iron ore with microwaves, the method uses microwaves as energy, super iron concentrate as raw material, coal dust as reducer, to produce high-purity sponge iron, and then smelting and blowing to produce 316L stainless steel 3D printing powder. Aiming at the problems of low purity of scrap steel raw materials, complex impurity components and the like in the prior art, the method for preparing the 3D printing metal powder by gas atomization of the 316L stainless steel based on the technology of reducing iron ore by microwaves is provided, the iron ore is heated by microwaves, high-purity sponge iron is reduced and smelted by coal dust to replace scrap steel, and the vacuum gas atomization process for preparing the 3D printing metal powder is realized, so that the manufacturing of the high-quality 3D printing metal powder is realized.

In addition, the metal 3D printing technology has the characteristics of high melt cooling speed, short formation time of molten pool tissues and the like, is expected to realize the precise formation of complex parts of oxide dispersion strengthening steel and complex structural parts of nuclear reactors, maintains ideal structural dimensions and distribution states of nano oxide particles, and maintains the advantages of the oxide dispersion strengthening steel in terms of tissues and performances. However, the current 3D printing oxide dispersion strengthening steel technology has been slow to develop, mainly due to the lack of high quality oxide dispersion strengthening steel powder raw materials available for 3D printing, as described above, the mechanically alloyed oxide dispersion strengthening powder obtained by high energy mechanical ball milling in the conventional method, the purpose of this process is nano oxide clusters in the powder, which is also the core and key for obtaining nano oxide dispersion particles later. However, high-energy ball milling can induce serious deformation of oxide dispersion strengthening steel powder, the powder after ball milling is generally in a flat shape or an irregular shape, the sphericity and the fluidity of the powder are obviously reduced, a large number of defects such as pores, cracks and the like appear in a 3D printing product, and even the phenomenon that the powder cannot be formed occurs.

At present, research groups at home and abroad mainly reduce the damage degree of mechanical alloying to the sphericity and fluidity of powder by changing ball milling parameters, however, the reduction of mechanical ball milling time or the reduction of ball milling energy input seriously affects the introduction of oxide nanoclusters, so that the performance of the 3D printing oxide dispersion strengthening steel product is far lower than that of the traditional powder metallurgy oxide dispersion strengthening steel. In this regard, attempts have been made at home to treat mechanically alloyed oxide dispersion-strengthened steel powders using plasma spheroidization techniques. The principle is that powder is melted by plasma, and sphericity and fluidity are improved by means of self spheroidization effect or modification of powder morphology, however, the method has two problems: (1) The nano clusters in the powder form oxide particles after melting, and the powder is subjected to secondary melting and solidification in the 3D printing process after spheroidization, so that the formed nano oxide particles grow up rapidly in the melt or burn out to form slag; (2) The technology has the problems of high cost, difficult large-scale production and the like, and limits the application of the technology in the production of oxide dispersion strengthening steel powder raw materials for 3D printing.

The spheroidizing method for the mechanically alloyed oxide dispersion-strengthened steel powder is still lacking at present, and low-cost preparation of the oxide dispersion-strengthened steel spherical powder for high-quality 3D printing is realized.

Disclosure of Invention

In view of the problems existing in the prior art, the invention aims to provide a preparation method of oxide dispersion strengthening steel spherical powder for 3D printing, which solves the problem of lack of oxide dispersion strengthening steel powder for high-quality 3D printing, breaks through the bottleneck of the development of the 3D printing oxide dispersion strengthening steel technology, and the obtained powder has sphericity of more than 75D1/da, granularity of 10-100 mu m, fluidity value of less than 20s/50g and oxygen content of less than 3500ppm.

To achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of oxide dispersion strengthening steel spherical powder for 3D printing, which comprises the following steps:

(1) Mixing the gas atomization prealloy powder and the rare earth oxide powder, and then performing high-energy ball milling to obtain oxide dispersion strengthening steel powder;

(2) Mixing the oxide dispersion strengthening steel powder obtained in the step (1) with a gas flow grinding medium, adding the mixture into a fluidized bed, and discharging air in the fluidized bed to obtain a material-carrying fluidized bed;

(3) Heating the material-carrying fluidized bed obtained in the step (2), introducing mixed gas after the fluidization state of the powder in the material-carrying fluidized bed is stable, controlling the flow of the mixed gas, cooling after the preset reaction time is reached, and obtaining the steel ball-shaped powder from the material-carrying fluidized bed.

The oxide dispersion strengthening steel ball powder for high-quality 3D printing is prepared by utilizing high-energy ball milling and a fluidized bed, and has the advantages of simple preparation process, low production cost, high efficiency, small impurity introduction amount, easy realization of engineering amplification and the like. The preparation of the oxide dispersion strengthening steel powder for high-quality 3D printing is realized by utilizing the synergistic effect between high-energy ball milling and a fluidized bed, the sphericity is more than 75D1/da, the granularity is 10-100 mu m, the fluidity value is less than 20s/50g, and the oxygen content is less than 3500ppm.

In the invention, the mixed gas is introduced into the cooling process for cooling for 10-30min, and then hydrogen is introduced into the cooling process for cooling, wherein the mixed gas is the mixed gas of argon, nitrogen, neon or helium and the like and hydrogen. The flow of nitrogen or inert gas in the mixed gas is 0.4-2m/min, and the flow of hydrogen is 0.1-1m/min. The flow rate of the hydrogen is 0.1-1.5m/min after cooling for 10-30 min.

The high-energy ball milling is a conventional means in the prior art.

As a preferable technical scheme of the invention, the gas atomization prealloy powder in the step (1) comprises a matrix Fe and alloying elements.

Preferably, the alloying element comprises 1 or a combination of at least 2 of Cr, ni, mo, W, ti, zr or Hf.

Preferably, in the gas-atomized prealloy powder in the step (1), the content of the matrix Fe is 40-95.5% by mass, and the balance is an alloy element, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 95.5%, etc., but not limited to the listed values, and other non-listed values in the range are equally applicable.

Preferably, the purity of the gas-atomized prealloyed powder in step (1) is > 98%, for example, 98.2%, 98.5%, 98.7%, 99%, 99.2%, 99.6% or 99.8%, etc., but not limited to the recited values, and other non-recited values within this range are equally applicable.

Preferably, the shape of the gas-atomized pre-alloy powder in the step (1) is spherical.

Preferably, the particle size of the gas-atomized prealloyed powder of step (1) is < 150. Mu.m, for example, 149. Mu.m, 147. Mu.m, 145. Mu.m, 142. Mu.m, 140. Mu.m, 135. Mu.m, 130. Mu.m, 125. Mu.m, 120. Mu.m, 115. Mu.m, 110. Mu.m, 105. Mu.m, etc., but not limited to the values recited, other values not recited in the range are equally applicable.

As a preferable technical scheme of the invention, the rare earth oxide powder in the step (1) comprises yttrium oxide powder.

Preferably, the particle size of the rare earth oxide powder in step (1) is less than 500nm, and may be 498nm, 496nm, 494nm, 492nm, 490nm, 488nm, 486nm, 484nm, 482nm, 480nm, 478nm, 476nm, 474nm, 472nm, 470nm, 450nm, 420nm, 400nm, 350nm or 300nm, for example, but not limited to the values recited, and other non-recited values within this range are equally applicable.

Preferably, the purity of the rare earth oxide powder in the step (1) is > 97%, for example, 97%, 97.5%, 98%, 98.2%, 98.5%, 98.7%, 99%, 99.2%, 99.6% or 99.8%, etc., but not limited to the recited values, and other non-recited values within this range are equally applicable.

As a preferred technical solution of the present invention, the mass ratio of the oxide dispersion strengthening steel powder and the air flow grinding medium in the mixing in the step (2) is > 3:1, for example, it may be 3.4:1, 3.6:1, 3.8:1, 4:1, 4.5:1, 5:1 or 6:1, etc., but not limited to the listed values, and other non-listed values in the range are equally applicable.

Preferably, the air flow grinding medium in the step (2) is spherical ceramic powder with higher hardness than oxide dispersion strengthening steel powder.

Preferably, the spherical ceramic powder is 1 or a combination of at least 2 of zirconia, alumina or tungsten carbide.

The particle size of the spherical ceramic powder is preferably 100 to 300. Mu.m, for example, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, or the like, but not limited to the recited values, and other non-recited values within the range are equally applicable.

The purity of the spherical ceramic powder is preferably > 99.9%, and may be, for example, 99.91%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98%, 99.99%, or the like, but is not limited to the recited values, and other non-recited values within this range are equally applicable.

Preferably, the purity of the spherical ceramic powder is > 99.99%, for example, 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998% or 99.999%, etc., but not limited to the recited values, and other non-recited values within this range are equally applicable.

Preferably, the material of the fluidized bed in the step (2) comprises high-purity quartz or stainless steel.

Preferably, the purity of the high purity quartz is equal to or greater than 99.5%, for example, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9%, etc., but is not limited to the recited values, and other non-recited values within this range are equally applicable.

Preferably, the air discharged from the fluidized bed in the step (2) is discharged in the form of a protective gas. Wherein the flow rate of the shielding gas is 0.2-2m/min. The charging time of the shielding gas is more than or equal to 50min.

Preferably, the shielding gas comprises nitrogen and/or an inert gas.

Preferably, the purity of the shielding gas is > 99.99%, for example 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998% or 99.999%, etc., but not limited to the recited values, other non-recited values within this range are equally applicable.

As a preferable technical scheme of the invention, the mixed gas in the step (3) comprises auxiliary gas and reducing gas.

Preferably, the reducing gas in the mixture is 0-30% by volume, and the balance is auxiliary gas, for example, 0%, 5%, 10%, 15%, 20%, 25% or 30%, etc., but not limited to the recited values, and other non-recited values in the range are equally applicable.

Preferably, the auxiliary gas comprises a gas that does not react with the oxide dispersion strengthened steel powder, preferably 1 or a combination of at least 2 of nitrogen, argon, neon or helium.

Preferably, the purity of the auxiliary gas is > 99.99%, for example 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998% or 99.999%, etc., but not limited to the recited values, other non-recited values within this range are equally applicable.

Preferably, the reducing gas comprises a gas which reacts with the impurity oxide in the oxide dispersion strengthening steel powder in a reducing way, and preferably hydrogen.

Preferably, the purity of the reducing gas is > 99.99%, for example 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998% or 99.999%, etc., but not limited to the recited values, other non-recited values within this range are equally applicable.

In a preferred embodiment of the present invention, the heating end point temperature in the step (3) is 400 to 850 ℃, and may be 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, or the like, for example, but the end point temperature is not limited to the values recited, and other values not recited in the range are equally applicable.

As a preferable embodiment of the present invention, the flow rate in the step (3) is 0.1-2m/min, for example, 0.1m/min, 0.2m/min, 0.4m/min, 0.6m/min, 0.8m/min, 1m/min, 1.2m/min, 1.4m/min, 1.6m/min, 1.8m/min or 2m/min, etc., but the flow rate is not limited to the recited values, and other non-recited values in the range are equally applicable.

In the invention, after stabilizing for 5-30min, the volume ratio of the auxiliary gas and the reducing gas in the mixed gas in the flow control can also be controlled by respective flow, the flow of the auxiliary gas is controlled to be 0.1-2m/min, and the flow of the reducing gas is controlled to be 0.1-1.5m/min.

As a preferable technical scheme of the invention, the preset reaction time in the step (3) is more than or equal to 15min, for example, 15min, 18min, 20min, 25min, 30min, 35min, 40min, 50min or 60min and the like, but the preset reaction time is not limited to the listed values, and other non-listed values in the range are applicable.

As a preferable embodiment of the present invention, the sphericity of the steel-ball-shaped powder obtained in the step (3) is > 75d1/da, and for example, 76d1/da, 77d1/da, 78d1/da, 79d1/da, 80d1/da, 85d1/da, 90d1/da, 100d1/da, etc., but not limited to the recited values, and other non-recited values within the range are equally applicable.

The particle size of the steel-ball-shaped powder obtained in the step (3) is preferably 10 to 100. Mu.m, for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc., but not limited to the values recited, and other values not recited in the range are equally applicable.

Preferably, the fluidity value of the steel ball-shaped powder obtained in the step (3) is less than 20s/50g, and may be, for example, 19s/50g, 18s/50g, 17s/50g, 16s/50g, 15s/50g, 14s/50g, 10s/50g or 5s/50g, etc., but not limited to the recited values, and other non-recited values within the range are equally applicable.

Preferably, the oxygen content of the steel ball-shaped powder obtained in the step (3) is less than 3500ppm, for example, 3400ppm, 3200ppm, 3000ppm, 2500ppm, 2000ppm, 1500ppm, 1000ppm, 500ppm, 100ppm or 10ppm, etc., but not limited to the recited values, other non-recited values within the range are equally applicable.

As a preferable technical scheme of the invention, the preparation method comprises the following steps:

(3) Heating the carrying fluidized bed obtained in the step (2) and introducing mixed gas, controlling the flow of the mixed gas after the fluidization state of the powder in the carrying fluidized bed is stable, and cooling after the preset reaction time is reached, so as to obtain the steel ball-shaped powder from the carrying fluidized bed;

in the step (2), the mass ratio of the oxide dispersion strengthening steel powder to the air flow grinding medium in the mixing is more than 3:1, and the air flow grinding medium is spherical ceramic powder with the hardness remarkably higher than that of the oxide dispersion strengthening steel powder;

the mixed gas in the step (3) comprises auxiliary gas and reducing gas, wherein the reducing gas accounts for 0-30% by volume percent, the balance is the auxiliary gas, the heating terminal temperature is 400-850 ℃, the flow is 0.1-2m/min, and the preset reaction time is more than or equal to 15min.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) The oxide dispersion strengthening steel powder prepared by the method has the advantages of higher sphericity, good fluidity, low impurity content and the like, meets the technical requirement of 3D investigation, breaks through the technical bottleneck that 3D printing and forming are difficult due to the lack of high-quality oxide dispersion strengthening steel spherical powder, and has sphericity of more than 75D1/da, granularity of 10-100 mu m, fluidity value of less than 20s/50g and oxygen content of less than 3500ppm.

(2) The method has the advantages of simple equipment and process, short treatment period and flow, high efficiency, stable powder quality, low production cost, easy scale-up and continuous operation, good industrialization prospect and the like.

Drawings

FIG. 1 is an SEM photograph of an oxide dispersion-strengthened steel powder raw material of example 1 of the present invention;

FIG. 2 is an SEM photograph of spherical steel powder obtained in example 1 of the present invention;

FIG. 3 is a photograph of an optical organization of a 3D printed product of application example 1 of the present invention;

FIG. 4 is an SEM photograph of the microstructure of a 3D printed product according to application example 1 of the present invention;

the present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.

Detailed Description

For a better illustration of the present invention, which is convenient for understanding the technical solution of the present invention, exemplary but non-limiting examples of the present invention are as follows:

example 1

Oxide dispersion strengthening steel powder with the component of Fe-16Cr-0.5Ti-0.5Y is selected as a raw material, the raw material is obtained by high-energy ball milling treatment according to a formula, and an SEM image is shown as in figure 1, so that the powder is in an irregular flat shape, has extremely poor sphericity and fluidity, and cannot be directly subjected to 3D printing.

100g of powder raw material is weighed and added into a fluidized bed, zirconia ceramic particles with the particle size range of 125-250 mu m are used as auxiliary media of an air flow mill, 10g of zirconia powder is weighed and added into the fluidized bed, argon is introduced into the fluidized bed to discharge air in the fluidized bed, and the air speed is 0.6m/min and the time is 60min. Placing the fluidized bed into a resistance furnace, ensuring that a powder raw material flowing area is positioned in a heating constant temperature area, an air inlet/outlet is far away from the heating area, stabilizing for 5min, reducing the flow rate of argon to 0.5m/min, and introducing hydrogen with the flow rate of 0.1m/min; and (3) raising the temperature in the resistance furnace to 600 ℃, observing the fluidization condition of the powder at the temperature raising rate of 10 ℃/min, determining stable fluidization, and then starting the air current grinding spheroidization treatment, wherein the control time is 60min.

After the experiment is finished, the resistance furnace is closed, the fluidized bed is taken out and placed on a fixed table for air cooling, the mixed atmosphere protection of argon and hydrogen is kept, the argon flow is 0.5m/min, the hydrogen flow is 0.1m/min, the hydrogen is stopped to be introduced after 10min, the argon flow is improved to 0.6m/min, after the fluidized bed is air cooled to room temperature, the argon is stopped to be introduced, powder is taken out from the fluidized bed, a standard mesh screen with 150 meshes and a standard mesh screen with 1500 meshes is selected for respectively screening out powder with the particle size not reaching the standard and zirconia powder, the oxide dispersion strengthening steel powder meeting the 3D printing particle size requirement is obtained, the SEM image is shown in figure 2, the morphology of the powder particles is approximately spherical, the particle size distribution range is 5-50 mu m, and the requirements of the 3D printing technology on the shape and the size of the powder raw materials can be obtained after screening.

The sphericity of the powder after the treatment was 78 (d 1/da) as measured by SEM, the flowability was 19.1s/50g as measured by a Hall flow meter, and the oxygen increment was 500ppm.

Example 2

This embodiment 2 is different from embodiment 1 in that: the components of the oxide dispersion strengthening steel powder in the embodiment 1 are converted from Fe-16Cr-0.5Ti-0.5Y ferrite to Fe-18Cr-8Ni-0.5Ti-0.5Y austenite, the air flow grinding time is reduced from 60min to 15min, the experimental temperature is increased from 600 ℃ to 850 ℃, and other experimental conditions are unchanged.

The sphericity of the powder after the treatment was 76 (d 1/da) as measured by SEM, the flowability was 19.8s/50g as measured by a Hall flow meter, and the oxygen increment was 1800ppm. It is explained that the change of the matrix and the components of the oxide dispersion strengthening steel powder does not significantly affect the implementation performance of the method, and the reduction of the air flow grinding time shortens the sphericizing time of the powder, but the increase of the temperature can promote the softening effect of the metal powder and reduce the hardness, thereby strengthening the sphericizing treatment effect of the powder.

Example 3

This embodiment 2 is different from embodiment 1 in that: the auxiliary medium of the jet mill in example 1 was changed from zirconia ceramic particles to tungsten carbide ceramic particles, 100g of the oxide dispersion-strengthened steel powder raw material was weighed, and 20g of the tungsten carbide ceramic particles were weighed because the tungsten carbide ceramic particles had a larger mass than the zirconia powder, and the oxide dispersion-strengthened steel powder raw material and the tungsten carbide ceramic particles were added to the fluidized bed.

The sphericity of the powder after the treatment was 81 (d 1/da) as measured by SEM, the flowability was 18.8s/50g as measured by a Hall flow meter, and the oxygen increment was 400ppm. Tungsten carbide has higher hardness than zirconia, so that the tungsten carbide has better effect when assisting the jet mill.

Application example 1

2000g of the oxide dispersion-strengthened steel powder obtained in example 1 was weighed and 3D-printed using AFS-M120 selective laser melting equipment model number manufactured by beijing brand automatic molding systems limited, with the following parameters: the high-purity argon gas is used for protecting, the oxygen partial pressure is 2000ppm, the laser power is 150W, the laser scanning speed is 500mm/s, the scanning interval is 40 mu m, the powder spreading thickness is 50 mu m, the sample specification is a cube of 10mm multiplied by 10mm, the forming quality and the structure of a 3D printing product of the oxide dispersion strengthening steel spherical powder are characterized by an optical microscope and a scanning electron microscope, as shown in fig. 3 and 4, the defects of holes, cracks and the like are different after the traditional non-spherical oxide dispersion strengthening steel powder is printed, and the 3D printing device of the oxide dispersion strengthening steel powder is obtained by the powder treatment method has few macroscopic defects and good tissue uniformity; as can be seen from fig. 4, a lot of nano-sized spherical oxide dispersion particles can be found in the material structure, the particle size is uniform, the distribution is very uniform, and the oxide dispersion strengthening steel powder obtained by adopting the powder treatment method of the invention can be subjected to 3D printing to obtain the typical nano-oxide dispersion strengthening structure of the oxide dispersion strengthening steel, so that the contradiction that the powder spheroidization/printing performance and the nano-oxide formation quality are difficult to coordinate in other spheroidization technologies is solved.

Comparative example 1

The difference from example 1 was only that the end point temperature of the heating was 900℃and the sphericity of the powder after SEM measurement was 78 (d 1/da), the flowability was 19.8s/50g as measured by a Hall flow meter, and the oxygen increment was 3650ppm. The reason for the excessive increase in oxygen content is that the powder is easily reflected in the residual oxygen in the high purity gas during the high temperature process.

Comparative example 2

The difference from example 1 was only that the flow rate of the control mixture (argon and hydrogen) was 3m/min, the sphericity of the powder after SEM measurement treatment was 72 (d 1/da), and the flowability was 20.2s/50g as measured by a Hall flow rate meter, while the particle size distribution of the powder was changed from 10 to 100 μm to 18 to 100. Mu.m. The reason is that the increase of the air flow reduces the contact frequency between the powder and between the powder and the air flow grinding medium, reduces the air flow grinding efficiency, and simultaneously the excessively high air speed blows out the powder with the particle size smaller than 18 mu m from the air outlet, so that the particle size range of the treated particles is narrowed.

Comparative example 3

The difference from example 1 is only that the flow rate of the control mixture (argon and hydrogen) is 0.03m/min, the sphericity of the powder after SEM measurement is 35 (d 1/da), and the fluidity is close to 0 as measured by a hall flowmeter, because the powder is not fluidized under the low air flow condition, and the fine powder is agglomerated and bonded under the high temperature condition, and finally the air flow grinding effect cannot be realized.

As can be seen from the results of the above examples and comparative examples, the oxide dispersion strengthening steel ball powder prepared by the method has the advantages of higher sphericity, good fluidity, low impurity content and the like, meets the requirements of 3D investigation technology, breaks through the technical bottleneck that the 3D printing and forming are difficult due to the lack of high-quality oxide dispersion strengthening steel ball powder, has sphericity of more than 75D1/da, granularity of 10-100 mu m, fluidity value of less than 20s/50g and oxygen content of less than 3500ppm.

The applicant states that the detailed structural features of the present invention are described by the above embodiments, but the present invention is not limited to the above detailed structural features, i.e. it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope of the present invention and the scope of the disclosure.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims

1. The preparation method of the oxide dispersion strengthening steel spherical powder for 3D printing is characterized by comprising the following steps of:

the mass ratio of the oxide dispersion strengthening steel powder to the air flow grinding medium in the mixing is more than 3:1; the air flow grinding medium is spherical ceramic powder with higher hardness than oxide dispersion strengthening steel powder;

(3) Heating the carrying fluidized bed obtained in the step (2), introducing mixed gas after the fluidization state of powder in the carrying fluidized bed is stable, controlling the flow of the mixed gas, cooling after reaching the preset reaction time, and obtaining the steel ball-shaped powder from the carrying fluidized bed;

the mixed gas comprises auxiliary gas and reducing gas, wherein the reducing gas is 0-30% by volume percent, and the balance is the auxiliary gas; the end temperature of the heating is 400-850 ℃; the flow is 0.1-2m/min; the preset reaction time is more than or equal to 15min;

the sphericity of the obtained steel ball-shaped powder is more than 75d1/da, the granularity is 10-100 mu m, the fluidity value is less than 20s/50g, and the oxygen content is less than 3500ppm.

2. The method of claim 1, wherein the gas atomized prealloy powder of step (1) includes a base Fe and an alloying element.

3. The method of manufacturing as claimed in claim 2, wherein the alloying element comprises 1 or a combination of at least 2 of Cr, ni, mo, W, ti, zr or Hf.

4. The method according to claim 1, wherein the base Fe in the gas-atomized prealloy powder in the step (1) is 40-95.5% by mass, and the balance is alloy elements.

5. The method of claim 1, wherein the purity of the aerosolized prealloyed powder of step (1) is > 98%.

6. The method of claim 1, wherein the gas atomized prealloy powder of step (1) is spherical in shape.

7. The method of claim 1, wherein the particle size of the gas atomized prealloy powder of step (1) is < 150 μm.

8. The method of claim 1, wherein the rare earth oxide powder of step (1) comprises yttria powder.

9. The method of claim 1, wherein the rare earth oxide powder of step (1) has a particle size of < 500nm.

10. The method of claim 1, wherein the rare earth oxide powder of step (1) has a purity of > 97%.

11. The method of claim 1, wherein the spherical ceramic powder is 1 or a combination of at least 2 of zirconia, alumina, or tungsten carbide.

12. The method of claim 1, wherein the spherical ceramic powder has a particle size of 100 to 300 μm.

13. The method of claim 1, wherein the spherical ceramic powder has a purity of > 99.9%.

14. The method of claim 13, wherein the spherical ceramic powder has a purity of > 99.99%.

15. The method of claim 1, wherein the fluidized bed in step (2) is made of high purity quartz or stainless steel.

16. The method of claim 15, wherein the purity of the high purity quartz is greater than or equal to 99.5%.

17. The method of claim 1, wherein the exhausting of air from the fluidized bed in step (2) is exhausting air in the form of introducing a shielding gas.

18. The method of claim 17, wherein the shielding gas comprises nitrogen and/or an inert gas.

19. The method of claim 17, wherein the shielding gas has a purity of > 99.99%.

20. The method of manufacturing according to claim 1, wherein the assist gas comprises a gas that does not react with the oxide dispersion-strengthened steel powder.

21. The method of claim 20, wherein the assist gas is 1 or a combination of at least 2 of nitrogen, argon, neon, or helium.

22. The method of claim 1, wherein the assist gas has a purity of > 99.99%.

23. The method of claim 1, wherein the reducing gas comprises a gas that undergoes a reduction reaction with an impurity oxide in the oxide dispersion strengthened steel powder.

24. The method of claim 23, wherein the reducing gas is hydrogen.

25. The method of claim 1, wherein the reducing gas has a purity of > 99.99%.